Process for oligomerising mono-olefins

ABSTRACT

A CATALYST FOR THE OLIGOMERISATION OF OLEFINS E.G. BUTENES TO OCTENES AND DODECENES, IS PREPARED BY CONTACTING SILLICA GEL SEQUENTIALLY WITH AQUEOUS SOLUTIONS CONTAINING (I) ALUMINIUM IONS, (II) ALKALI METAL IONS, (III) NICKEL IONS IN THAT ORDER, AND THEN ACTIVATING THE CATALYST BY HEATING IN AIR OR AN INERT GAS TO 400-1000*C. THE OLIGOMERS HAVE A LOW DEGREE OF BRANCHING, AND ARE PRODUCED BY CONTACTING THE CATALYST WITH THE OLEFIN AT A TEMPERATURE FROM 0 TO 300*C. AND A PRESSURE FROM 0 TO 5000 P.S.I.G.

United States Patent 3,816,555 PROCESS FOR OLIGOMERISING MONO-OLEFINSKeith George Allum, Bracknell, England, assignor to The BritishPetroleum Company, Limited, London, England No Drawing. Originalapplication June 4, 1970, Ser. No. 43,554, now Patent No. 3,729,428.Divided and this application June 6, 1972, Ser. No. 260,192 Claimspriority, application Great Britain, June 17, 1969, 30,578/ 69 Int. Cl.C07c 3/20 U.S. Cl. 260-683.15 R 3 Claims ABSTRACT OF THE DISCLGSURE Acatalyst for the oligomerisation of olefins e.g. butenes to octenes anddodecenes, is prepared by contacting silica gel sequentially withaqueous solutions containing (i) aluminium ions, (ii) alkali metal ions,(iii) nickel ions in that order, and then activating the catalyst byheating in air or an inert gas to 400-1000 C. The oligomers have a lowdegree of branching, and are produced by contacting the catalyst withthe olefin at a temperature from 0 to 300 C. and a pressure from 0 to5000 p.s.i.g.

This is a division of application Ser. No. 43,554, filed June 4, 1970,now U.S. Pat. No. 3,729,428.

This invention relates to a novel catalyst composition, its process ofpreparation and its use in the oligomerisation of olefins.

British patent specification 1,069,296 discloses a process for theproduction of dimers which process comprises dimerising an olefin in thepresence of a catalyst prepared by (a) contacting silica gel or amaterial containing silica gel, the silica bearing hydrogen atoms insurface hydroxyl groups capable of ionising and exchanging, with anaqueous ionic solution of a salt of aluminium, under conditions suchthat aluminium ions are incorporated onto the surface of the silica gelto form a catalyst precursor base, (b) contacting the solid oxide eitherbefore or after incorporation of the aluminium ions with an aqueoussolution containing nickel ions under conditions such that nickel ionsare incorporated onto the surface of the oxide to form with thealuminium and silica gel, a catalyst precursor and (c) activating thecatalyst precursor to form a catalyst.

It has now been found that such nickel/aluminium/ silica catalysts canbe further improved by the addition of alkali metal ions, particularlywhen the alkali metal ions are added before the nickel ions.

Thus according to one aspect of the present invention there is provideda catalyst precursor comprising silica gel having thereon ions of themetals (i) aluminium, (ii) one or more of the alkali metals and (iii)nickel.

According to another aspect of the present invention there is provided aprocess for the preparation of a catalyst precursor which processcomprises (1) contacting silica gel, the silica gel bearing hydrogenatoms in surface hydroxyl groups capable of ionising and exchanging,with an aqueous ionic solution of a salt of aluminium, under conditionssuch that aluminium ions are incorporated into the surface of the silicagel to form a catalyst precursor base, (2) subsequently contacting thecatalyst precursor base with an aqueous solution containing alkali metalions under conditions such that alkali metal ions are incorporated ontothe surface of the catalyst precursor base and (3) subsequentlycontacting the catalyst precursor base with an aqueous solutioncontaining nickel ions under conditions such that nickel ions areincorporated onto the surface of the oxide to form with the aluminiumand silica gel, a catalyst precursor.

In the case of the nickel/aluminium/silica catalyst, for

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highest activity with maximum selectivity to low branched products it isnecessary to have a nickelzaluminium atomic ratio close to 0.5. Thisrequires careful prolonged treatment of aluminium/silica with the nickelsalt solution and is somewhat difiicult to achieve especially on a largescale. It is an advantage of the present invention that for highselectivity to desired products it is not essential to employ such ahigh nickelzaluminium ratio. The overall catalyst preparation istherefore easier despite the addition of a further step.

Thus according to another aspect of the present invention there isprovided a process for the oligomerisation of olefins which processcomprises contacting an olefin under oligomerisation conditions -with acatalyst prepared by (l) contacting silica gel, the silica bearinghydrogen atoms in surface hydroxyl groups capable of ionising andexchanging, with an aqueous ionic solution of a salt of aluminium, underconditions such that aluminium ions are incorporated onto the surface ofthe silica gel to form a catalyst precursor base, (2) subsequentlycontacting the catalyst precursor base with an aqueous solutioncontaining alkali metal ions under conditions such that alkali metalions are incorporated onto the surface of the catalyst precursor base,(3) subsequently contacting the catalyst precursor base with an aqueoussolution containing nickel ions under conditions such that nickel ionsare incorporated onto the surface of the oxide to form with thealuminium and silica gel, a catalyst precursor and (4) activating thecatalyst precursor to form a catalyst.

Each contact may be carried out at temperatures from 0 to 110 C.,preferably ambient temperature. After each contact with a solution thesilica gel should be thoroughly washed with de-ionised water to removeany impregnated salt. Again this washing may be at 0 to C., and isdesirably continued until the wash water is free of metal ions.

By this method it is believed that a reduction in the number of freeacidic aluminium-silica sites is obtained. It is believed that sodiumions replace the acidic protons associated with the aluminium on thesurface of the silica and that subsequent contact with a solutioncontaining nickel ions results in a high proportion of the sodium beingreplaced by nickel. Any aluminium exchanged silica site not associatedwith nickel is believed to be effectively blocked for polymerisation bythe presence of sodium. If nickel is exchanged onto the silica gelbefore the alkali metal, a less active catalyst is produced.

The silica gel may be prepared from an aqueous solution of a solubleinorganic or organic silicate by hydrolysis, followed by drying andcalcining at 250-600 C. A gel formed in this way will contain hydrogenatoms in surface hydroxyl groups capable of ionising and exchanging.

It is advantageous in the preparation to pretreat the silica gel beforeit is used for exchange. A suitable pretreatment procedure is asfollows:

(a) Wash with 2 N nitric acid or N hydrochloric acid.

(b) Wash thoroughly with water.

(c) Heat to 550 C. for up to three days under air or nitrogen.

It is also advantageous in the preparation to treat the aluminium saltsolution used for exchange in such a way as to maximise the pH of thesolution. This may be obtained in the case of an aluminium sulphatesolution by percolation through a bed of alumina.

Preferably the solution of the aluminium salt has an initialconcentration not less than M/ 20.

Preferably contacting with the solution of the aluminium salt iscontinued until 0.1 to 5% by weight, expressed as a percentage by weightof the silica gel, of

the aluminium ion is incorporated onto the surface of the silica.

Preferably the solution has an initial pH in the range 2 to 3.8, beingless than that at which the hydroxide is formed.

The preferred aluminium salt from which the aluminium ions are obtainedis aluminium sulphate but the nitrate is also suitable.

The aluminium exchanged silica can also be prepared by the treatment ofsilica with aluminium triethyl and hydrolysing the product.

Suitable alkali metal containing solutions can be prepared frombicarbonates, carbonates and chlorides. The alkali metal solution can beof any initial concentration up to the saturation concentration. Thetime of contact is preferably limited to a maximum of hours, to avoiddamage to the silica.

Preferably the amount of alkali metal added is from 0.1 to 5% by weightexpressed as a percentage by weight of the silica gel, more particularly0.1 to 2% wt. The preferred alkali metal is sodium.

Suitable nickel containing solutions may be prepared from water solublesalts of nickel, e.g., nickel nitrate, sulphate or chloride, and thecomplexes formed when normally water insoluble compounds, e.g., nickelformate are dissolved in aqueous ammonia.

Preferably the nickel solution has an initial concentration not lessthan M/ 100.

Preferably contacting with the nickel solution is continued until 0.1-5%by weight, expressed as percent by weight of the silica gel, of nickelions is incorporated onto the surface of the silica. Preferably thenickel content is 0.1 to 2% wt.

Activation is achieved by heating in air or an inert gas to atemperature in the range 400-1000 C. Preferably activation is at 450-700C. and the time of heating is /2 hour or longer although at the highertemperatures shorter activation times may be possible.

The particle size of the catalyst is governed by the particle size ofthe silica gel initially taken and can be of any size convenient to theoligomerisation procedure. It is desirable to start with a high surfacearea silica gel to obtain high activity, i.e., preferably a surface areagreater than 100 square metres per gram.

The oligomerisation process of the present invention is preferablycarried out at a temperature between 0 C. and 300 C. and at a pressureof between atmospheric and 3000 p.s.i.g. in either a batch process or acontinuous process. Preferably the pressure is such that liquid phaseconditions are maintained in the reaction zone. Preferred temperaturesand pressures are 15 to 200 C. and atmosphere to 2000 p.s.i.g.

In a batch process the oligomerisation is preferably carried out at acatalyst concentration of between 1 g. and 200 g. of catalyst per litreof olefin in the feed.

In a continuous process the oligomerisation is preferably carried out ata weight hourly space velocity of between 0.01 and 20 g. of olefin feedper g. of catalyst per hour.

Low molecular weight gaseous or liquid mono-olefins containing 2-10carbon atoms or any mixtures of these may be oligomerised. Theoligomerised products contain a high proportion of dimers, although sometrimers and tetramers are produced.

Preferred feedstocks are propylene and butenes, butene- 2 givingoligomers with a greater degree of branching than butene-l. The catalystis particularly useful for the conversion of mixtures of propylene andbutenes to a range of olefins containing 6 to 8 carbon atoms for theconversion of n-butenes into dodecenes. With feedstocks containing ahigh proportion of butene-I there may be some isomerisation of it tobutene-2. This reaction is exothermic and heat may have to be withdrawnfrom the system to control the temperature. The presence of a diluentwill also help in controlling the temperature rise.

The oligomerisation may be carried out in the presence of a diluent.Suitable diluents are hydrocarbons, e.g., parafiinic hydrocarbons suchas n-heptane or cyclohexane and aromatic hydrocarbons such as toluene.Commercial olefin streams frequently contain alkanes. Their presence hasbeen found not to be detrimental and they may, as indicated above, bebeneficial in some instances as a diluent.

The invention is illustrated by the following examples.

EXAMPLE 1 A catalyst was prepared as follows. Four hundred g. of silicagel was acid washed with 4 litres of 2 N nitric acid during 6 hours andwas then washed with 12 litres of water. After being heated to 550 C. inair for 3 days the silica was placed in a column and an alumina-treatedM/l0 aluminium sulphate solution (pH 3.6-3.7) was slowly percolatedthrough the column. The percolation was continued until the solutioncoming out of the column had a pH of 3.53.6 (approximately 7 days). Thesilica was washed with water in a Soxhlet apparatus for 3 days. Sodiumwas exchanged onto the aluminium/silica by the percolation of 1 litre ofM/ 10 sodium bicarbonate solution through the silica followed by a 3 daywater wash in a Soxhlet apparatus. Nickel was exchanged for sodium onthe silica by the slow percolation of M/ 10 nickel nitrate solutionthrough a bed of the exchanged silica for 14 days. After water washingin a Soxhlet apparatus for 3 days and drying at 120 C., the catalyst wasactivated at 550 C. in a stream of nitrogen for 4 hours. The catalystcontained 1.45 percent by weight of aluminium, 0.36 percent by weight ofsodium, and 0.70 percent by weight of nickel.

Part of the catalyst (18 g.) was used to oligomerise butene-l at C. and800 p.s.i.g. in a 1 litre rocking autoclave for 18 hours. The liquidoligomers (172 g.) were found to consist of 82 percent by weight ofoctenes, 14 percent by weight of dodecenes, and 4 percent by weight ofhigher molecular weight oligomers. The activity of the catalyst was 0.54g. of product per g. of catalyst per hour. The octenes were found toconsist of 27 percent by weight of 3,4-dimethylhexenes, 53 percent byweight of 3-methylheptenes, 18 percent by weight of noctenes, and 2percent by weight of other structures. This represents an average of1.11 branches per molecule. The dodecenes had an average of 2.76branches per molecule.

EXAMPLE 2 A part of the catalyst prepared in Example 1 (118 g.) was usedto oligomerise butene-l in daily batches at 80 C. and 800 p.s.i.g. in a3 litre rocking autoclave for 24 consecutive days. The activity of thecatalyst decreased from 0.20 g. of product per g. of catalyst per hour(1st day) to 0.14 g. of product per g. of catalyst per hour (24th day).Of the liquid oligomers, 65 percent by weight was octenes on the firstday and this rose to 85 percent by weight on the 24th day. The averagedegree of branching of the octenes decreased from 1.24 (1st day) to 0.92(24th day) and of the dodecenes from 3.05 (1st day) to 2.16 under theseconditions. A substantially longer half life might be expected underconditions of continuous operation.

EXAMPLE 3 In this example 9 g. of catalyst containing 0.89 percent byweight of aluminium, 0.02 percent by weight of sodium, and 0.75 percentby weight of nickel, was used to oligomerise butene-l at 80 C. and 800p.s.i.g. in a 1 litre rocking autoclave for 22 hours. Liquid oligomers(319 g.) were obtained representing an activity of 1.61 g. of productper g. of catalyst per hour. The composition of the products was asfollows, percent by weight of octenes, 15 percent by weight of dodecenesand 5 percent by weight of olefins of higher molecular weight. Theoctenes had the followingstructures, 18 percent by weight of3,4-dimethylhexenes, 69 percent by weight of 3-methylheptenes, and 13percent by weight of n-octenes. This represents an average of 1.07branches per molecule. The dodecenes had an average of 2.46 branches permolecule.

EXAMPLE 4 In this example the catalyst was prepared by taking a nickeland aluminium exchanged silica gel and adding a small amount of sodiumby impregnation. The catalyst contained 0.29 percent by weight ofaluminium, 0.20 percent by weight of nickel, and 0.05 percent by weightof sodium. The catalyst (21 g.) had an activity of 0.15 g. of productper g. of catalyst per hour when used to oligomerise butene-1 at 80 C.in a 1 litre rocking autoclave for 20 hours. The oligomers (62 g.) werefound to consist of 85 percent by weight of octenes. The octenes had thefollowing composition, 17 percent by weight of 3,4-dimethylhexenes, 61percent by weight of 3-methylheptenes, 20 percent by weight ofn-octenes, and 2 percent by weight of other structures. This representsan average of 0.99 branches per molecule. This catalyst, which wasprepared by adding the sodium after the nickel, was less active thancatalysts in which the sodium was exchanged before the nickel.

EXAMPLE 5 A catalyst was prepared containing 0.80 percent by weightnickel, 0.90 percent by weight aluminium and 0.02 percent by weightsodium and was activated in air at 55 0 C. for 70 hours. Part of thiscatalyst g.) was used for propylene oligomerisation in a 1 litre rockingautoclave at 85 C./750 p.s.i.g. for 4 hours. An activity of 4.0 g./g./h. was observed. Products consisted of dimers 86 percent Weight, ofwhich 31.0 percent was n-hexenes and 64.5 percent was methylpentenes,trimers 11.7 percent and tetramers and other heavier oligomers 2.1percent.

EXAMPLE 6 EXAMPLE 7 Part (14 g.) of the catalyst used in Example 6 wasused for propyleneoligomerisation in a continuous flow system. Propylenewas passed over the catalyst in the liquid phase at a rate of 2.0vol./vol./h. at 700 p.s.i.g. Temperature was increased from 76 C. to155C. during the course of the experiment. Propylene conversion tooligomers was over 90 percent weight. The product distributions observedat the various temperatures are summarised in the following table.

Temperature,C 76 84 121 125 155 Percent weight:

Dlmers 70.3 62.8 37.5 33.8 32.9 Trimers 20.8 25.6 31.0 31.2 39.3Tetramers,etc 8.9 11.6 31.5 35.0 27.8 Dimer fraction:

n-Hexenes 29.0 32.1 49.2 51.2 60.7 Methylpentenes 64.5 60.8 45.5 43.835.7

EXAMPLE 8 A catalyst was prepared containing 0.62 percent weight nickel,0.74 percent weight aluminium and 0.11 percent weight sodium. Part ofthis catalyst 102 g.) was used for butene oligomerisation in a flowsystem. The butene feed contained 74 percent weight butene-2 and 24percent weight butene-l. This feed was passed over the catalyst in theliquid phase at a space velocity of 2.0 vol./vol./h. at 1000 p.s.i.g.and at a temperature of C. Butene conversion to oligomers was 47 percentweight and the selectivity to octenes was 81 percent weight. The octeneshad the following composition, 37 percent weight of 3,4-dimethylhexenes, 46 percent weight of 3-methylheptenes, 11 percentweight of n-octenes and 6 percent weight of other structures. Thisrepresents an average of 1.30 branches per molecule.

EXAMPLE 9 The catalyst used in Example 8 was used for oligom erisationof a mixture of butenes and propylene which also contained unreactivebutanes. The feed composition, was 19 percent weight of propylene, 12percent weight of butene-1, 3 percent of isobutene, 34 percent weight ofbutene-2 and 32 percent weight of butanes. A flow system was used forthis reaction and the feed was passed over the catalyst in the liquidphase at a space velocity of 3.0 vol./vol./h. at 1000 p.s.i.g. and 150C. The total olefin conversion to oligomers was 46 percent and thecomposition of the product was 22 percent weight of hexenes, 37 percentweight of heptenes, 20 percent weight of octenes and 21 percent weightof higher boiling material. The average number of branches per moleculein the C -C olefins was 1.24.

I claim:

1. A process for the oligomerisation of olefins comprising contacting afeedstock containing at least one mono-olefin having from 2 to 10 carbonatoms at 0 to 300 C. and atmospheric to 3000 p.s.i.g. pressure with acatalyst prepared by 1) contacting silica gel, the silica gel bearinghydrogen atoms in surface hydroxyl groups capable of ionising andexchanging, with an aqueous ionic solution of a salt of aluminium, underconditions such that aluminium ions are incorporated onto the surface ofthe silica gel to form a catalyst precursor base, (2) subsequentlycontacting the catalyst precursor base with an aqueous solutioncontaining alkali metal ions under conditions such that alkali metalions are incorporated onto the surface of the catalyst precursor base,(3) subsequently contacting the catalyst precursor base with an aqueoussolution containing nickel ions under conditions such that nickel ionsare incorporated onto the surface of the silica gel to form withaluminium, alkali metal, and silica gel a catalyst precursor, the silicagel being thoroughly washed with de-ionised water after each contactingoperation to remove any impregnated salt and the amounts of aluminium,alkali metal and nickel added each being within the range 0.1 to 5% bywt., all by weight of the silica gel, and (4) activating the catalyst byheating same in a stream of air or an inert gas to a temperature in therange 400 to 1000 C.

2. A process as claimed in claim 1 wherein the oligomerisationtemperature is from 15 to 200 C. and the pressure from atmospheric to2000 p.s.i.g.

3. A process as claimed in claim 2 wherein the feedstock containspropylene, a butene, or both propylene and at least one butene.

References Cited UNITED STATES PATENTS 2,331,233 4/1959 can; 260-683.153,005,033 10/1951 Engelbrecht et al. 260-683.15 3,557,242 1/1971 Sampsona a1. 260-68315 FOREIGN PATENTS 1,069,296 5/1967 Great Britain 260683.15

PAUL M. COUGHLAN, JR., Primary Examiner mg 7 UNITED STATES PATITNTOFFICE V CERTIFICATE OF CORRECTION Que 3,816,555 Wed June 11, 1974Inventor) Keith George Allum It is certified that error appear-o in theabove-identified patent and that; said Letters Patent are herebycorrected as shown below:

Column 5, line 16, change "80C" to 80C psig Signed and sealed this 1stday of October1 197 c- (SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

